Blount0 soil had never received glyphosate prior to the incubation. The initial, small increase in soil respiration on Blount0 might be due to toxic effects on some microorganisms sensitive to glyphosate whose detritus provided a readily available C substrate. The negative impact is supported by the overall respiration because subsequent to the initial respiration increase, the respiration in Blount0 decreased dramatically compared to the control. This could be due to the reduction in total microbial biomass and or an inability of the community to fully function in the presence of glyphosate. This is in line with our previous study, where the application of glyphosate decreased the total microbial biomass of the soybean rhizosphere soil that had no previous exposure to glyphosate (Lane et al. 2012). Similarly, Araújo et al. (2003) reported higher soil respiration is reported in soils with previous glyphosate application history, compared to the soils that had no glyphosate exposure.